AIRMAR B765LH Chirp Ready Thru Hull Transducer Instruction Manual

AIRMAR B765LH Chirp Ready Thru Hull Transducer

Product Information

The product is a Thru-Hull Mount Retractable with Valve Chirp Transducer. It is available in three models: B765LH, B765LM, and B785M. The transducer is designed for use in boats with fiberglass or wood hulls and is not suitable for metal hulls due to the risk of electrolytic corrosion. The transducer requires the installation of a High-Performance Fairing for optimal performance and sealing.

Warnings

• A High-Performance Fairing must be installed following the provided instructions. An anti-rotation bolt is required to prevent the fairing from turning while the boat is underway.
• Always wear safety glasses, a dust mask, and ear protection during installation.
• Check for leaks immediately after placing the boat in the water. Do not leave the boat unchecked for more than three hours as even a small leak can lead to significant water accumulation.
• For B744V and B744VL models, ensure that the paddlewheel insert or blanking plug, along with the insert nut and safety wire, are properly installed to achieve a watertight seal.
• All O-rings must be intact and well lubricated for a watertight seal. Do not attempt to install the insert without lubricating all the O-rings as it may damage them.
• Attach the safety wire to prevent the insert from backing out in case of failure or incorrect installation of the cap nut and/or insert nut.
• Do not remove the CAP nut as it will cause the valve assembly to come out. The insert or blanking plug cannot be secured without the valve assembly.
• Never pull, carry, or hold the sensor by its cable to avoid severing internal connections.
• Operate the transducer only in water to prevent overheating and failure.
• Do not install a metal housing in a vessel with a positive ground system.
• Avoid striking the sensor to prevent damage.
• Avoid using solvents, cleaners, fuels, sealants, or other products that may contain solvents as they can damage plastic parts, especially the transducer’s face.
• Do not power sand or pressure wash the sensor as it may weaken the structure or damage internal components.

Important Installation Instructions

• Read the instructions completely before proceeding with the installation. These instructions supersede any other instructions in your instrument manual if they differ.
• The sensor must be installed with a High-Performance Fairing for proper sealing. A fairing that matches the shape of the hull should be carefully cut to provide a sealing surface around the drilled hole. Failure to install the sensor with a fairing may result in insufficient sealing, leading to water leakage and potential damage or sinking of the boat.

Applications
The bronze sensor is recommended for use in fiberglass or wood hulls only. It is not suitable for mounting in a metal hull due to the risk of electrolytic corrosion.

Tools & Materials Required

• High-Performance Fairing (MANDATORY)
• Safety glasses
• Dust mask
• Ear protection
• Grommet(s) (required for some installations)
• Cable ties
• Water-based anti-fouling coating (mandatory for saltwater installations)

Product Usage Instructions

1. Ensure you have all the necessary tools and materials mentioned above.
2. Read the entire installation instructions carefully before starting the installation process.
3. If installing the B744V or B744VL models, ensure that the paddlewheel insert or blanking plug, insert nut, and safety wire are properly installed to achieve a watertight seal.
4. Lubricate all O-rings of the insert before attempting to install it. Do not dry fit the insert in the housing.
5. Attach the safety wire to prevent the insert from backing out in case of failure or incorrect installation of the cap nut and/or insert nut.
6. Do not remove the CAP nut as it will cause the valve assembly to come out. The insert or blanking plug cannot be secured without the valve assembly.
7. Ensure the boat is placed in the water immediately after installation to check for any leaks. Do not leave the boat unchecked for more than three hours.
8. Never pull, carry, or hold the sensor by its cable to avoid damaging internal connections.
9. Operate the transducer only in water and avoid operating it in air to prevent overheating and failure.
10. Avoid striking the sensor and do not use solvents, cleaners, fuels, sealants, or other products that may contain solvents as they can damage plastic parts.
11. Do not power sand or pressure wash the sensor as it may weaken the structure or damage internal components.
12. Follow the specific instructions provided for installing the High-Performance Fairing to ensure proper sealing and performance.

Safety Instruction

Follow the precautions for optimal product performance and to reduce the risk of property damage, personal injury, and/or death.

• WARNING: A High-Performance Fairing must be installed following the installation instructions that accompany the fairing. A High-Performance Fairing requires an anti-rotation bolt to keep the fairing from turning while the boat is underway.
• WARNING: Always wear safety glasses, a dust mask, and ear protection when installing.
• WARNING: Immediately check for leaks when the boat is placed in the water. Do not leave the boat unchecked for more than three hours. Even a small leak may allow considerable water to accumulate.
• WARNING: B744V, B744VL—The valve is not a watertight seal! Always install the paddlewheel insert or the blanking plug secured with the insert nut and safety wire for a watertight seal.
• WARNING: B744V, B744VL—All the O-rings must be intact and well lubricated to make a watertight seal. Do not dry fit the insert in the housing. Attempting to install the insert without lubricating all the O-rings may damage them, possibly preventing full insertion and a watertight seal.
• WARNING: B744V, B744VL—Always attach the safety wire to prevent the insert from backing out in the unlikely event that the cap nut and/or insert nut fails or is screwed on incorrectly.
• WARNING: B744V, B744VL—Do not remove the CAP nut. The valve assembly will come out. The insert or blanking plug cannot be secured without the valve assembly.
• CAUTION: Never, pull, carry, or hold the sensor by its cable. This may sever internal connections.
• CAUTION: Always operate the transducer in water. Operating in air will allow the transducer to overheat resulting in failure.
• CAUTION: Never install a metal housing in a vessel with a positive ground system.
• CAUTION: Never strike the sensor.
• CAUTION: Never use solvents. Cleaner, fuel, sealant, and other products may contain solvents that can damage plastic parts, especially the transducer’s face.
• CAUTION: Never power sand or pressure wash the sensor. It may weaken the structure or damage the internal components.
• IMPORTANT: The sensor must be installed carefully. Read the instructions completely before proceeding with the installation. These instructions supersede any other instructions in your instrument manual if they differ.

WARNING
The sensor must be installed with a High-Performance Fairing!

• A fairing that is carefully cut to fit the shape of the hull provides a sealing surface around the drilled hole. If the sensor is not installed with a fairing, there may be insufficient surface area to seal the hull. Water may leak into the boat causing damage or possibly sinking.

What’s In The Box

Applications

Bronze sensor recommended for fiberglass or wood hull only. Never mount a bronze housing in a metal hull because electrolytic corrosion will occur.

Tools & Materials

• High-Performance Fairing (MANDATORY)
• Safety glasses
• Dust mask
• Ear protection
• Grommet(s) (some installations)
• Cable ties
• Water-based anti-fouling coating (mandatory in saltwater)

Identify Your Model
The model name is printed on the cable tag.

Pretest: B744V, B744VL
Connect the multisensor to the instrument and spin the paddlewheel. Check for a speed reading and the approximate air temperature. If there is no reading or it is inaccurate, check the connections and repeat the test. If there is still no reading or they are inaccurate, return the product to the place of purchase.

Record the information found on the cable tag for future reference.

• Part No.___Date_Frequency____kHz

Mounting Location

Guidelines

• CAUTION: Do not mount the sensor in line with or near water intake or discharge openings or behind strakes, fittings, or hull irregularities that will disturb the water flow.
• CAUTION: Do not mount the sensor where the boat may be supported during trailering, launching, hauling, or storage to avoid damaging the transducer’s face.
• The water flowing under the hull must be smooth with a minimum of bubbles and turbulence, especially at high speeds.
• The sensor must be continuously immersed in water at all speeds.
• The transducer beam must be unobstructed by the keel or propeller shaft(s).
• Choose a location away from interference caused by power and radiation sources such as: the propeller(s) and shaft(s), other machinery, other echosounders, and other cables. The lower the noise level, the higher the echosounder gain setting that can be used.
• Choose a location with a minimum deadrise angle.
• Choose an accessible spot inside the vessel with adequate headroom for the height of the housing, tightening the nut(s), and installing any insert.
  • Model/Min. with fairing
  • B744V 255mm (10″)
  • B744VL 381mm (15″)
• Chirp transducer —Mount in a cool well-ventilated area away from the engine to avoid overheating.

Boat Types (Figure 1)

• Displacement hull powerboat —Locate 1/3 of the way along the LWL and 150 to 300mm (6–12″) off the centerline. The side of the hull where the propeller blades are moving downward is preferred.
• Planing hull powerboat —Mount well aft near the centerline and well inboard of the first set of lifting strakes to ensure that it is in contact with the water at high speeds. The side of the hull where the propeller blades are moving downward is preferred.
  • Outboard and I/O —Mount forward and to the side of the engine(s).
  • Inboard —Mount well ahead of the propeller(s) and shaft(s).
  • Stepped hull —Mount just ahead of the first step.
  • Boats capable of speeds above 25kn (29MPH) —Review sensor location and operating results of similar boats before proceeding.
• Fin keel sailboats —Mount to the side of the centerline and forward of the fin keel 300 to 600mm (1–2′).
• Full keel sailboats —Locate amidships and away from the keel at the point of minimum deadrise angle.

Installation

Installation: B744V, B744VL

Installing the Cap Nut
CAUTION: Avoid cross threading the CAP nut.

Being sure the valve assembly is seated firmly within the housing, carefully screw the CAP nut in place (Figure 2). Hand-tighten only. Do not over tighten.

Installing the Paddlewheel Insert

1. All the O-rings must be intact and well lubricated to make a watertight seal. After the sealant cures, inspect the O-rings on the paddlewheel insert (replace if necessary) and lubricate them with the silicone lubricant supplied (Figure 3).
2. Slide the paddlewheel insert into the housing with the arrow on the top pointing forward toward the bow. Seat it into place using a twisting motion until the keys fit into the notches. (The insert fits one way only.) Be careful not to rotate the outer housing and disturb the sealant. Screw the INSERT nut in place and hand-tighten only. Do not over tighten.
3. Attach the safety wire to prevent the insert from backing out in the unlikely event that the cap nut and/or insert nut fails or is screwed on incorrectly. Wrap one end of the safety wire tightly around the stem of the housing and twist it together with the long end (Figure 2). Keeping the wire taut throughout, lead the wire straight up and through one eye in the CAP nut. Thread the wire through the eye a second time. Lead the wire in a counterclockwise direction and thread it through the eye in the INSERT nut. Thread the wire through that eye a second time. Loop the wire through the pull ring and twist the wire securely to itself.

Cable Routing & Connecting

CAUTION:
If the sensor came with a connector, do not remove it to ease cable routing. If the cable must be cut and spliced, use Airmar’s splash-proof Junction Box No. 33-035 and follow the instructions supplied. Removing the waterproof connector or cutting the cable, except when using a watertight junction box, will void the sensor warranty.

1. Route the cable to the instrument, being careful not to tear the cable jacket when passing it through the bulkhead(s) and other parts of the boat. Use grommets to prevent chafing. To reduce electrical interference, separate the sensor cable from other electrical wiring and the engine. Coil any excess cable and secure it in place using cable ties to prevent damage.
2. Refer to the echosounder owner’s manual to connect the sensor to the instrument.

Check for Leaks
When the boat is placed in the water, immediately check around the sensor for leaks. Note that very small leaks may not be readily observed. Do not leave the boat in the water for more than 3 hours before checking it again. If there is a small leak, there may be considerable bilge water accumulation after 24 hours. If a leak is observed, repeat “Bedding” and “Installing” immediately (High-Performance Fairing Installation Instructions).

Operation & Maintenance

Anti-fouling Coating
Surfaces exposed to saltwater must be covered with an anti-fouling coating. Use a water-based anti-fouling coating made for transducers only. Never use ketone-based paint, since ketones can attack many plastics possibly damaging the transducer. Brush on anti-fouling coating every 6 months or at the beginning of each boating season.

B744V/VL—Coat the following surfaces (Figure 4):

• Exposed areas of the housing including the transducer’s face
• Bore of the housing up 30mm (1-1/4″)
• Outside wall of the paddlewheel insert below the lower O-ring
• Paddlewheel cavity
• Paddlewheel
• Blanking plug below the lower O-ring including the exposed end

Cleaning the Sensor
Aquatic growth can accumulate rapidly on the sensor’s surface, reducing its performance within weeks. Clean the surface with mild household detergent and a Scotch-Brite® scour pad.

B744V/VL
If fouling on the insert is severe, push out the paddlewheel shaft using a spare shaft or a 4-D finish nail with a flattened point. Then lightly wet sand the paddlewheel with fine grade wet/dry paper.

How the Valve Works: B744V/VL

WARNING: The valve is not a watertight seal!
Always install the paddlewheel insert or the blanking plug secured with the INSERT nut and safety wire for a watertight seal.

The multisensor incorporates a self-closing valve which minimizes the flow of water into the vessel when the paddlewheel insert is removed (Figure 3). The curved flap valve is activated by both a spring and water pressure. Water pushes the flap valve upward to block the opening, so there is no gush of water into the boat.

Using the Blanking Plug: B744V/VL
To protect the paddlewheel, use the blanking plug:

• When the boat will be kept in saltwater for more than a week.
• When the boat will be removed from the water.
• When aquatic growth buildup on the paddlewheel is suspected due to inaccurate readings from the instrument.

1. All the O-rings must be intact and well lubricated to make a watertight seal. On the blanking plug, inspect the O-rings (replace if necessary) and lubricate them with silicone lubricant or petroleum jelly (Figure 3).

2. Remove the paddlewheel insert from the housing by removing the safety wire from the pull ring and the INSERT nut (Figure 2). Unscrew the INSERT nut. Do not remove the CAP nut, as the valve assembly will come out.

3. Grasp the pull ring and remove the paddlewheel insert with a slow pulling motion.
   NOTE: In the unlikely event that the paddlewheel insert cannot be removed, see “Servicing the Valve Assembly” below.

4. Slide the blanking plug into the housing. Seat it into place with a pushing twisting motion until the keys fit into the notches (Figure 3). Screw the INSERT nut in place and hand-tighten only. Do not over tighten.

5. Reattach the safety wire (Figure 2).

Servicing the Valve Assembly: B744V/VL

WARNING:
The insert/blanking plug cannot be secured without the valve sleeve. When the valve assembly is removed, always re-insert the valve sleeve secured with the CAP nut and the insert/blanking plug secured with the INSERT nut and safety wire for a watertight seal.

CAUTION:
Be careful to avoid cross threading the CAP nut.

Should the valve fail, it will need to be removed for servicing. Follow the steps below. If a new valve assembly is required and not immediately available, the valve sleeve must be reinstalled in the multisensor housing for a watertight seal. Remove the flap valve, spring pin, and spring from the sleeve (Figure 5). Then reinstall the sleeve in the housing.

1. All the O-rings must be intact and well lubricated to make a watertight seal. On the blanking plug, inspect the O-rings (replace if necessary) and lubricate them with silicone lubricant or petroleum jelly (Figure 3).

2. Remove the safety wire and unscrew the CAP nut (Figure 2).
   With the blanking plug ready in one hand, remove the paddlewheel insert and valve assembly as one unit by grasping the pull ring and pulling upward. Rapidly replace the valve assembly with the blanking plug to minimize the flow of water into the boat. Temporarily secure it with the safety wire. Do not leave the boat in the water unattended. This is not a watertight or secure seal!

3. Separate the paddlewheel insert from the valve assembly by unscrewing the INSERT nut (Figure 3). Grasp the pull ring and pull slowly upward.

4. Clean, repair, or replace the valve assembly so the flap valve moves freely and seats against the sleeve (Figure 5).

5. To reinstall the valve assembly, inspect the O-rings on the paddlewheel insert (replace if necessary) and lubricate them with silicone lubricant or petroleum jelly to make a watertight seal (Figure 3).

6. Slide the paddlewheel insert into the valve assembly. Seat it in place with a twisting motion until the keys fit into the notches. Secure the paddlewheel insert with the INSERT nut. Handtighten only. Do not over tighten.

7. Remove the safety wire from the multisensor. With the combined valve assembly and paddlewheel insert ready in one hand, remove the blanking plug. Slide the assembly into the multisensor housing with the arrow on the top pointing forward toward the bow. Be sure the cable fits into the cable channel and the notch in the sleeve fits into the key in the housing (Figure 5). (A pushing twisting motion will locate the key.) Screw the CAP nut in place, being careful to avoid crossthreading. Hand-tighten only. Do not over tighten.

8. Reattach the safety wire (Figure 2).

Servicing the Paddlewheel Insert: B744V/VL
The water lubricated paddlewheel bearings have a life of up to 5 years on low- speed boats [less than 10kn (11MPH)] and 1 year on high-speed vessels. Paddlewheels can fracture and shafts can bend due to impact with water borne objects and mishandling in boat yards. O-rings must be free of abrasions and cuts to ensure a watertight seal.

1. Using the new paddlewheel shaft, push out the old shaft about 6mm (1/4″). With pliers, remove the old shaft (Figure 3).
2. Place the new paddlewheel in the cavity with the flat side of the blade facing the same direction as the arrow on the top of the insert.
3. Tap in the new shaft into place until the ends are flush with the sides of the insert.
4. All the O-rings must be intact and well lubricated to make a watertight seal. Install two O-rings in the lower groves near the paddlewheel. Do not place them near the pull ring.
5. Being sure the O-rings are intact and well lubricated to make a watertight seal, the remaining two O-rings are placed in a similar position on the blanking plug.
6. To reinstall the paddlewheel insert, see “Installing the Paddlewheel Insert” (page 2).

Winterizing: B744V/VL
After the boat has been hauled for winter storage, remove the blanking plug to let the water drain away before reinserting it. This will prevent any water from freezing around the blanking plug and possibly cracking it.

Replacement Sensor & Parts

• The information needed to order a replacement Airmar sensor is printed on the cable tag. Do not remove this tag. When ordering, specify the part number, date, and frequency in kHz. For convenient reference, record this information at the bottom of page one.
• Lost, broken, and worn parts should be replaced immediately. Obtain parts from your instrument manufacturer or marine dealer.

Gemeco USA

• Tel: 803-693-0777
• Email: sales@gemeco.com.

Airmar EMEA

Europe, Middle East, Africa

• Tel: +33.(0)2.23.52.06.48
• Email: sales@airmar-emea.com.

35 Meadowbrook Drive, Milford, New Hampshire 03055-4613, USA www.airmar.com.

Copyright © 2004 2021 Airmar Technology Corporation.

References

• emea.com
• airmar.com
• airmar.com/patent.html

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